The subject matter disclosed herein relates generally to components and assemblies of gas turbine engines, and more particularly to such components and assemblies used in bypass fans.
A turbofan gas turbine engine used for propelling an aircraft includes a fan assembly having a plurality of circumferentially spaced apart fan blades extending radially outwardly from a rotor disk. Airflow is channeled between the blades and pressurized thereby for generating thrust for powering the aircraft. The fan assembly typically includes a plurality of circumferentially spaced apart fan blades each having a dovetail root disposed in a complementary, axially extending dovetail groove or slot in a perimeter or rim of a rotor disk. The dovetail grooves are defined by dovetail posts and are complementary in configuration with the blade dovetail roots for radially retaining the blades to the rotor disk. The blades are also axially retained in the rotor disk to prevent axial movement of the blades in the upstream and downstream directions. A spinner is mounted to a front end of the fan assembly to provide smooth airflow into the fan. A radially inner flowpath boundary for the airflow channeled between the blades is provided typically by integral or non-integral platforms at the blade roots.
It is often a goal to increase airflow through the fan assembly to increase thrust. This thrust increase may be accomplished by increasing the radius of the fan blade tip. However, this fan blade change impacts both a rotating airfoil and the radially adjacent fan case, adding weight at a high radial location that must be borne by the fan assembly rotor hardware during operation. Other options exist to increase airflow without increasing the fan blade tip radius. The inner flowpath boundary, often referred to as the hub, can be moved radially inwardly thus getting designated as a low radius hub. However, low radius hubs present assembly challenges between the platforms and disk as the inner flowpath boundary tends to meet the top of the disk dovetail posts at the forward end of the disk, thus limiting the space for platform interface and mounting features.
Additionally, fan assemblies, in particular fan blades, are tested against various impact and high dynamic loading events, such as bird impacts and loss of fan blade events. It is often a goal to minimize the portion of a fan blade released during such impacts and events. During these events, the platform generally makes contact with the fan blade surface, raising the opportunity for fan blade damage and potential release of fan blade portions. It would be desirable to minimize the damage and potential release of fan blade portions.
There remains a need for an improved fan platform that incorporates features to permit a low radius hub design while minimizing the damage and potential release of fan blade portions during bird impacts and loss of fan blade events.